Adaptive integral sliding mode control for spacecraft attitude tracking with actuator uncertainty

The attitude tracking of a rigid spacecraft with actuator uncertainties, such as actuator faults, alignment errors, and saturation constraints is examined. In addition, the unknown external disturbances and spacecraft inertia are also taken into consideration. A novel integral-terminal-sliding mode (ITSM), which is singularity free compared to traditional TSM, is designed such that the attitude tracking error converges to zero in finite time on the ITSM. An adaptive technique is then utilized to develop an adaptive ITSM controller (AITSMC), which achieves finite-time attitude tracking in the presence of some or all of the above uncertainties. Numerical examples are presented to demonstrate the effectiveness of the proposed method.